Assembly of externally accessible brushes

ABSTRACT

Assembly of externally accessible brushes in an electric motor for power tools using an electric motor. The brushes are part of a brush holder assembly which also includes a holder having an internally threaded member portion of predetermined diameter, a tube carried in the holder, the brush radially slidable in the tube, and a coil spring carried on the brush. A retainer extends across the upper portion of the holder by a small predetermined dimension and is adapted to be radially depressed into the upper portion of the holder by means of a plunger or other suitable depresser such as a finger. The retainer acts to compress the spring and urge the brush downwardly, whereby the edges of the retainer are deflected into the threads of the holder. A cap is screw connected into the upper portion of the housing thereafter, with the retainer acting to isolate the spring from the turning motion of the cap, which might otherwise entangle the coils of the spring within the threads. Also, if a metal disc is attached to the brush by a wire to entrap the spring therebetween, the retainer permits the use of a simplified disc which is nonrotatable into assembled position by the retainer. The plunger acts to align and hold the spring out of contact with the holder during depression of the retainer within the holder.

United States Patent 91 Duncan et a1.

[ Nov. 19, 1974 ASSEMBLY OF EXTERNALLY ACCESSIBLE BRUSHES [75] Inventors: John L. Duncan, Pickens; Fredrick W. Duthie, Greenville, both of SC. [73] Assignee: The Singer Company, New York,

[22] Filed: Feb. 21, 1973 [21] Appl. No.: 334,492

[52] U.S. Cl. 310/242, 310/247 [51] Int. Cl. H02k 13/00 [58] Field of Search 310/239, 242, 245-247, 310/219, 229

[56] References Cited UNITED STATES PATENTS 672,604 4/1901 Lundell 310/239 1,273,647 7/1918 Moore 2,889,530 6/1959 Straub 310/247 3,239,704 3/1966 Miller 310/247 3,308,321 3/1967 Provost 310/245 3,329,844 7/1967 Happe 310/239 3,617,786 11/1971 Stielper 310/242 3,628,051 12/1971 Chigirnshy 310/247 Primary Examiner-R. Skudy Attorney, Agent, or Firm-Marshall J. Breen; Chester A. Williams, Jr.; Harold Weinstein [5 7] ABSTRACT Assembly of externally accessible brushes in an electric motor for power tools using an electric motor, The brushes are part of a brush holder assembly which also includes a holder having an internally threaded member portion of predetermined diameter, a tube carried in the holder, the brush radially slidable in the tube, and a coil spring carried on the brush. A retainer extends across the upper portion of the holder by a small predetermined dimension and is adapted to be radially depressed into the upper portion of the holder by means of a plunger or other suitable depresser such as a finger. The retainer acts to compress the spring and urge the brush downwardly, whereby the edges of the retainer are deflected into the threads of the holder. A cap is screw connected into the upper portion of the housing thereafter, with the retainer acting to isolate the spring from the turning motion of the cap, which might otherwise entangle the coils of the spring within the threads. Also, if a metal disc is attached to the brush by a wire to entrap the spring therebetween, the retainer permits the use of a simplified disc which is nonrotatable into assembled position by the retainer. The plunger acts to align and hold the spring out of contact with the holder during depression of the retainer within the holder.

8 Claims, 37 Drawing Figures 64 I46 my f I30 56 at... Q l F t7 //i //r A, --|32 I lllii I I/ l/ /7 68 us 88 66 ua 3 142 I28 144 PATENTEL rwv 1 .914

sum ear 4 'Fig. l3

4 7 B M. A w 6 A ASSEMBLY OF EXTERNALLY ACCESSIBLE BRUSHES BACKGROUND OF THE INVENTION FIG. 13 is a sectional view of the brush holder assem- Heretofore, in motors having externally accessible 5 bly showing a double cap.

brushes assembly required special care for prevention of entanglement of the spring within the threads of the screw cap and holder so as to avoid premature failure of the brushes. In order to avoid such failures, some brush holder assemblies eliminated the use of threaded connections and instead used higher priced holders or other components which were resilient and relied on interference fits to maintain assembled position. Another expensive way to avoid the brush spring entanglement or twisting during assembly was to use a metal disc having a non-turnable car which was inserted into the tube to protect the spring from the turning action of the cap.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved assembly for externally accessible brushes which overcomes the prior art disadvantages; which is simple, economical and reliable; which uses a retainer made of thin, nonmetallic and flexible material to isolate the spring from the cap; which uses a plunger to align the spring depression of the retainer within the holder; and which uses circular or noncircular retainers, the edges of which, are oversized from that of the diameter of the threaded holder whereby such edges will be crushed into the treads of the holder by inserting the plunger into the holder to depress the retainer.

Other objects and advantages will be apparent from the following description of several embodiments of the invention, and the novel features will be particularly pointedout hereinafter in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS This invention is illustrated in the accompanying drawings in which:

FIG. I is a perspective view of a power tool using an electric motor having externally accessible brushes therein and embodying the present invention.

FIG. 2 is a partial side elevational view of the brush holder assembly.

FIG. 3 is a side elevational view of apparatus for retaining the brush in a brush holder assembly and shows the retainer prior to insertion in the holder.

FIG. 4 is a side elevational view of an apparatus for retaining a brush in a brush holder assembly showing the retainer depressed within the holder.

F IG. 5 is a partial elevational view of the brush holder assembly showing the clamshell housing of the tool.

FIG. 6 is a side elevational view, in section, of the brush holder assembly.

FIG. 7 is a view taken along line 77 of FIG. 6.

FIG. 8 is an enlarged view showing the edge of the retainer crushed within the threads of the the holder shown in FIG. 6.

FIG. 9 is an exploded view, partly in section, of the brush holder assembly, including a plunger means.

FIG. 10 is a partial sectional view of a brush holder assembly using a shortened holder.-

FIG. 11 is a sectional view of a brush holder assembly having a brush spring of uniform diameter showing the retainer prior to insertion into the holder.

FIGS. 14-18 show various shapes of retainers as follows: FIG. 14 shows a rectangular retainer; FIG. I5 shows a retainer having four projecting tabs; FIG. 16 shows a retainer having a star shape; FIG. 17 shows a triangular retainer; and FIG. 18 shows a circular retainer having a central projection.

FIG. 19 shows the retainer of FIG. 18 in a sectional view of the brush holder assembly wherein the spring has an enlarged upper coil which fits around the projectron.

FIG. 20 shows a circular retainer having an integrally formed finger or plunger.

FIG. 21 shows the retainer of FIG. 20 atop the holder prior to depression therein.

FIG. 22 shows the retainer of FIG. 20 assembled in a brush holder assembly.

FIG. 23 shows a rectangular retainer having an integrally formed finger.

FIG. 24 shows the retainer of FIG. 20 with the finger inserted within the coils of the spring and the retainer atop the holder.

FIG. 25 shows the retainer of FIG. 20. depressed within the holder.

FIG. 26 shows a sectional view of the brush holder assembly and plunger using a modified brush, wherein the retainer sits atop the holder.

FIG. 27 is a sectional view showing the retainer of FIG. 26 inserted in the holder.

FIG. 28 shows the assembled brush holder assembly of FIG. 26 after removal of the plunger.

FIG. 29 shows a sectional view of a modified brush and plunger for a brush holder assembly with the retainer sitting atop the holder.

FIG. 30 shows the view of FIG. 29 wherein the retainer has been depressed into the holder.

FIG. 31 is an elevational view showing the brush holder assembly of FIG. 29 completely assembled.

FIG. 32 is an elevational view of a modified brush showing the retainer atop the holder and the plunger seated thereon.

FIG. 33 is an elevational view of FIG. 32, showing the retainer inserted into the holder.

FIG. 34 is an elevational view of an assembled brush holder assembly of FIG. 29 with the plunger removed.

FIG. 35 is an elevational view of the brush holder assembly of FIG. 32, with the plunger removed.

FIG. 36 is an elevational view of FIG. 35 with the retainer depressed within the holder.

FIG. 37 is a perspective view of the brush including the metallic disc wire and spring used in FIGS. 32-36.

DESCRIPTION OF THE INVENTION A conventional power tool, such as a sabre saw 40 is shown in FIG. 1 to embody the present invention, one form of which is illustrated in FIGS. 1-9.

The sabre saw 40 is powered by an electric motor of the commutator type, designated generally 42, which is mounted in a clamshell housing 44 having a support portion 46 and a cover portion 48 clamped together by suitable means. The motor 42 is operated by an on-off switch 50 shown in FIG. 1, and includes an armature 52 illustrated in FIG. 2 mounted on an armature shaft 54 journaled in the housing 44, which shaft also carries a commutator 56. A field core or stator 58 is disposed about the armature and affixed to the housing 44 as by screws 60.

A pair of diametrically opposed brush holder assemblies 62 are affixed to the housing 44 and carry brushes 64 biased to contact the commutator 56 as explained more fully hereinafter.

The brush holder assembly 62 shown in FIGS. 2, and 6, includes a nonmetallic holder 66, a metallic tube 68, a brush 64, a spring 112 and one or more caps 72. The holder 66 has an intermediate flange 74 which extends from either side of the body to terminate in an outwardly curved edge 76, the midpoint of which has a semicircular recess 78. The opposed flanges 74 have common sides 80 as shown in FIGS. 7 and 9. The holder 66 is mounted in a housing cavity 82 formed in equal halves in the support 46 and cover portion 48. The cavity 82 has a recess 84 into which resilient plugs 86 are disposed prior to the flange 74 being disposed therein whereby the recesses 78 lock against the plugs 86 to form a solid clamping connecting of the holder 66 upon the housing 44 being assembled.

The lower portion 88 of the holder 66 is cylindrical and has a circular opening 90 therein having four vertical grooves 92 set at 45 to the flat side 80 of the flanges 74 for receiving and positioning the tube 68 nonrotatable fashion. The upper portion 94 of the holder 66 is of somewhat larger diameter than the lower portion 88 and extends over the sides 80 of the flange 74. The upper portion 94 is counterbored to define a shoulder 96 at its base adjacent the level of the upper surface of the flanges 74, with the interior surface above the shoulder 96 threaded as at 98 along its entire radial surface. The term radial is used herein with reference to the radius of either the armature shaft 54 or the commutator 56 affixed thereto, to which the holder 66 is mounted in superposition and therefore, the term radial will correspond to the longitudinal or axial dimension of the holder 66. The tube 68 is shaped to be received within the lower portion 88 of the holder 66 with the most common shapes used being square, rectangular or round, and in the present instance is depicted as square. The tube 68 is made of metal and has a pair of tabs 100 formed on opposite sides of the upper edge to be bent downwardly and seat upon the shoulder 96 to limit the downward radial motion of the tube 68. An ear 102 is formed on one side of the bottom edge of the tube 68 which, after insertion into the lower portion 88, will be bent outwardly and prevent upwardremoval of the tube 68 from the holder 66. The ear 102 is also used to connect an electrical conductor 104 for carrying current in the usual manner as shown in FIG.

5. The tube 68 extends slightly outwardly and below the lower portion 88 of the holder 66, so as to facilitate the connection of the electrical conductor which may be by means of solder or suitable mechanical interference fit.

The brushes 64 used will determine the size and shape of the tube 68 and holder 66, so that the various components of the brush holder assembly 62 are compatible with one another. In the embodiment of the invention illustrated in FIGS. 1-9, the brushes 64 are substantially square in cross section with the bottom edge 106 concavely shaped to conform with the radial curve of the commutator 56. An aperture 108 is formed in the upper edge 110 into which the bottom coils of reduced diameter of a spring 112 are forced. This type of brush 64 may be termed a hole-in-head brush. The friction fit between the lower coils of spring 112 within the aperture 108 serve to connect the spring 112 and the brush 64. The upper coils of the spring 112 are enlarged to aid in trapping the upper part of the spring within the holder 66.

In a conventional brush holder assembly, the holder would be connected to the motor housing with the tube placed within the holder; the brush and connected spring would be disposed within the tube. and thereafter, a suitable cap would be connected to the holder to complete the assembly. However, experience has shown that such a construction leads to certain major difficulties, which it is the object of the present invention to overcome. Whether a single or double cap is used, the act of screwing the cap into the holder frequently causes the spring to tilt and crumple to one side, wherein the spring gets entangled with the threads and consequently affects the brush spring pressure and brush travel leading to premature failure of the motor 40.

In the present invention, these prior art difficulties are overcome by the use of an improved-brush holder assembly 62 which includes a retainer 114 in addition to the other conventional components thereof. The retainer 114 is made of a thin, nonmetallic and semiflexible material, as for example a heavy paper, or cardboard or fiber reinforced pressed board or plastic. The retainer 114 illustrated in the embodiment of the invention shown in FIGS. 1-9 is circular and has an outer diameter, slightly larger than the diameter of the threaded portion 98 of the upper portion 94 of the holder 66. FIG. 3 shows the retainer 114 sitting atop the upper portion 94 of the holder 66 prior to insertion therein. A central aperture 116 is provided in the retainer 114 to aid in insertion and removal of the re-' tainer 114. The outer periphery of the retainer 114 defines an edge 118 normally lying in the plane of the retainer 114 prior to insertion thereof in the holder 66.

A plunger means, designated generally 120, is associated with the retainer 114 and in combination with the retainer 114 may be termed an apparatus 122 for retaining a brush in a holder 66. The plunger means is illustrated in FIGS. 3, 4 and 9, and includes a barrel 124 having a central aperture 126 counter-bored at 128 to fonn an upper chamber 130, the topmost end of which is threaded to receive a cover 132. A plunger 134 having an enlarged head 136, a shank portion 138, extending from the head 136 to terminate in a tapered tip 140, is shown in the central aperture 126 of the barrel 124. The head 136 engages the shoulder 142 formed at the base of the upper chamber 130, while approximately one-half of the shank 138 extends out of the barrel 124. A plunger spring 144 is disposed in the upper chamber with one end engaging the cover 132 and the other end engaging the head 136 to normally bias the plunger 134 outwardly of the barrel 124. The end 146 of the barrel 124 opposite the cover 132 is substantially flat and lies in a plane perpendicular to the plunger 134.

While the brush holder assembly 62 may be assembled at any time, one convenient way of doing it is to assemble the tool 40 and the housing 44 with the holder 66 and tube 68 connected therein prior to the remainder of the components of assembly 62 being connected.

This is possible so long as the holder 66 is externally accessible with reference to the housing 44. Of course, it is always possible to preassemble the complete brush holder assembly 62 whenever it is desirable to so do. The holder 66 illustrated in FIG. 3 has been mounted within the housing 44, as shown in FIG. 5, but the housing is not shown in FIG. 3 for clarity of presentation. The tube 68 is disposed within the holder with the brush 64 and connected spring 112 radially slid therein to lightly engage the commutator 56. The upper end of the spring 112 extends to about the top of the holder 66 with the retainer 114 resting thereon. The plunger 134 is inserted in the aperture 116 of the retainer 114, and also into the interior of the coils of the spring 112, to place the tapered tip 140 into the aperture 108 of the brush 64. The end 146 will rest upon the upper surface of the retainer 114 and the operator will grasp the barrel 124 and move it in the direction of the commutator 56 to force the retainer to bottom against the tabs 100 of the tube 68, while radially compressing the spring 112 which slides downwardly along the shank 138 of the plunger 134. The plunger 134 remains stationary during insertion of the retainer 114, while the barrel 124 moves downwardly thereof to place the head 136 in a raised position within the upper chamber 130 and affect slight compression of the spring 144 therein, as is illustrated in FIG. 4. After removal of the plunger means 120, the retainner 114 will remain in its inserted position within the upper portion 94 of the holder 66, because the edge 118 thereof has been crushed within the threads 98 as best seen in FIG. 8. The upper last coil of the spring 112 extends outwardly of the tab 100 and is trapped between the shoulder 96 of the tube 66 and the retainer 114. A top plan view of the retainer 114 is shown in FIG. 7, wherein the edges 118 have been crushed and are caught in the threads 98. To complete the assembly, the screw cap 72 are threadedly received in the upper portion 94 of the holder 66, as illustrated in FIG. 6. A side elevational view of the completed brush holder assembly 62 is shown in FIG. 5, wherein the electrical conductor 104 is connected to the ear 102 of the tube 68.

It is possible to use a modified holder 66a in a housing 44a which serves as a lower portion for the holder with a built-in frame member 148 having a shoulder 150 to receive the bottom of the holder 66a and upon which the tabs 100 of the tube 68 will rest, and below which a radial recess 152 is formed in the frame 148 to hold and support the lower portion of the tube 68. The brush holder assembly 62a illustrated in FIG. 10, will be preassembled within the housing 44a prior to insertion of the brush 64 and connected spring 112. Thereafter, the brush 64 and spring 112 will be radially slidably disposed within the tube 68, and the retainer 114 inserted in the holder 66a as was illustrated in FIGS. 3 and 4. The threaded connection of the caps 72 will complete the assembly of the brush holder assembly 62a.

Another embodiment of the invention is shown in FIGS. 11, 12 and 13. A brush holder assembly 62b is shown in FIGS. 11 and 13 to include a spring 112b having a top coil of the same diameter as the remainder of the spring. other than this change, the assembly 62b is the same as that shown for the brush holder assembly 62. Accordingly, after mounting the holder 66 and tube 68 within the housing (not shown), the brush 64 will be radially received within the tube 68 with the connected spring 112b thereabove. The retainer 114 can be either pre-loaded upon the plunger means or placed atop the upper portion 94 of the holder 66 so that it is disposed above the spring ll2b into which the plunger 134 is inserted to align the spring "2b. Thereafter, the end 146 will engage the retainer 114 as illustrated in FIG. 12, to cause the same to be depressed into the upper portion 94 of the holder 66 to compress the spring ll2b which slides radially downwardly along the plunger 134 and causes the brush 64 to assume its operative position upon the commutator 56 with the retainer 114 maintaining its position due to the edges 118 thereof being crushed in the threads 98 of the holder 66. After removal of the plunger means 120, the assembly of the brush holder 6212 will be completed upon the threaded connection of the cap 72, as illustrated in FIG. 13.

The principle requirements for the retainer 114 are that it be made from a thin, nonmetallic and semiflexible material which can then be shaped in any of a number of configurations so long as the overall dimensions exceed the inner diameter of the holder 66 at the threads which receive the screw cap 72. Several configurations of an unlimited numer of possibilities for the shape of the retainers are shown in FIGS. 14-18. A retainer 114a is depicted in FIG. 14, and has four comers 154, connected by flat sides to define a rectangle or square having at least one longitudinal dimension greater than that of the inner diameter of the upper portion 94 of the holder 66. In assembled position, the retainer 1 14a would have its corners 154 distorted and bent into engagement with the threads 98 to maintain the retainer 114a in depressed position within the holder 66. Retainer ll4b illustrated in FIG. 15, has a circular periphery 156 from which tab 158 extends outwardly every 90. The diameter of the periphery 156 is smaller than the diameter of the threaded portion of the holder 66 into which the retainer 114b is inserted. However, the length measured from tab to tab will be slightly larger than the threaded diameter of the upper portion 94 of the holder 66, so that upon insertion of the retainer 114b within the holder 66, the tab 158 will be crushed within the threads 98 of the holder 66.

Retainer 114e, shown in FIG. 16, includes a starshaped outer periphery 160, with the distance measured between diametrically opposite star points exceeding the diameter of the threaded portion 94 of the holder 66, whereby the star point will be jammed within the threads upon insertion of the retainer l14c. A triangular-shaped retainer 114d is illustrated in FIG. 17, which has comers 162 having an effective length in in excess of the diameter of the threaded portion 94 of the holder 66, so that if placed upon the upper surface thereof, the retainer 114d would rest upon the same. Insertion of the retainer 114d within the holder 66 will cause the comer 162 to be crushed within the threads 98 of the holder 66.

A retainer 1 142 having a circular edge 118e, is shown in FIG. 18. The edge 118'e extends from-an annular body 164 lying in a single plane from which an annular projection 166 extends downwardly from the inner end thereof to form a second, smaller annular body 168 lying in a spaced, parallel plane with respect to the plane of body 164. The second annular projection 166 defines a recess 170 of which the body 168 serves as a base.

' ated use with a plunger means 120, or to aid in removal of the respective retainers.

In the embodiment of the invention depicted in FIG. 19, the retainer l14e is shown sitting atop the upper portion 94 of the holder 66 with the enlarged upper coil of the spring 112 seated about the projection 166, which faces downwardly. The brush 64 is slidably disposed within the tube 68 to nest within the holder 66 whereby on radially shifting the retainer l14e from the solid line top position shown in FIG. 19 to the dotted line bottom position at the base of the upper portion 94, the edges 118e to be crushed within the thread 98 of the holder 66 for purposes described hereinbefore. The spring 112 is aligned during depression of the retainer 1142 by being held about the projection 166 which can therefore be likened to the plunger. In this way, the retainer 114e will define an apparatus l22e which serves to retain the brush 64 within the holder 66 and aids in forming brush holder assembly 62e. If desired, the retainer ll4e could be turned over and the spring 112 replaced with the spring 112b, so that the top coils of the spring ll2b would fit within the now upwardly extending projection 166 to be seated within the recess 170 to effect alignment of the spring prior to depression of the retainer ll4e within the holder 66.

Additional modified retainers are shown in FIGS. 20-25. A retainer ll4f having a circular edge ll8f ia illustrated in FIG. 20. A downturned radial finger or plunger 170 is formed by slotted aperture l16f cut out on three sides with the last side 172, serving as a hinge to connect the plunger 170 to the retainer ll4f. Retainer ll4f defined as apparatus 122f which can be .used to retain a brush within a holder. FIG. 21 shows the retainer ll4f disposed upon the top of a holder 66 with the edges 1l8f extending slightly over the internal diameter of the upper portion 94. The plunger 170 is disposed within the inner coil of the spring 112b so as to keep the spring radially disposed during insertion of the retainer ll4f within the holder 66, and is shown in FIG. 22 by means of an assemblers finger or other device. The edges 118f are crushed within the threads 98 of the holder 66, and serve to prevent the retainer ll4f raising from its inserted position.

In certain electric motors, it is desirable to use a modified brush 64a having a circular post 174 rising above the topmost surface and about which the bottom coils of the spring are disposed to connect the same to the brush, as illustrated in FIG. 24. Once again, a retainer ll4f is used with its plunger 170 disposed within the inner coils of spring 112b, so as to remove any possibility of the coils from being caught within the threads 98 of the holder 66. Depression of the retainer ll4f by a finger or otherwise will cause the spring ll2b to compress, and the plunger 170 to collapse upon contacting the post 174 of the brush 64a. As was previously noted, the edge 118f will be crushed within the threads 98 of the holder 66 to maintain the spring ll2b in compressed position.

A rectangular retainer 114g is shown in FIG. 23 and defines an apparatus 122g which may be used for retaining a brush within a holder. A slot 116g is cut from one of the short sides to form a finger or plunger 176 with the inner end hinged to the body of the retainer 114g as at 178. The dimension of the larger side will be slightly greater than the inner diameter of the upper portion 94 of the holder 66, whereby on insertion into the threaded portion of the holder 66, the small sides will collapse within threads 98 of the holder 66 in a manner similar to that described hereinbefore.

A modified embodiment of the invention is shown in FIGS. 26-28, wherein a brush holder assembly 6211 is shown using the brush 64a and spring ll2b with the tube 68 and the holder 66. A retainer 114 is placed atop the holder 66 and the plunger 134 of the plunger means is inserted through the retainer 114 into the inside of the coil of the spring 112b to rest upon the post 174, as shown in FIG. 26. Insertion of the retainer 114 within the holder 66 upon depressing the barrel 124 of the plunger means 120 acts to compress the spring 1 12b to place the brush 64a in operative position upon the commutator 56 as shown in FIG. 27. After removal of the plunger means 120, the caps 72 will be threadedly received in the upper portion 94 of the holder 66, as is illustrated in FIG. 28.

Another modified brush holder assembly 621' is depicted in FIGS. 29, 30 and 31. A brush 64i having a hollow post 179 formed on the upper surface thereof and about which a spring ll2bis disposed. A retainer is placed upon the top' of the holder 66 with the spring 112b lightly touching the bottom portion thereof. A plunger means 120i is used to depress the retainer 114. Plunger means 120i has a solid barrel 124i with a flat lower edge 146i with a plunger 134i extending from the center thereof. The plunger 134i passes through aperture 116 to be received within the coils of spring 112b, as shown in FIG. 29. Insertion of the plunger means 120i within the upper portion 94 of the holder 66 results in the plunger 134i extending into the hollow center of the post 179 upon the spring 1l2b being compressed and the retainer 114 being depressed within the holder 66, as shown in FIG. 30. The edge 118 of retainer 114 will be crushed within the thread 98 of the upper portion 94 of the holder 66. After removal of the plunger means 120i, the threaded caps 72 will be connected to the holder 66, as shown in FIG. 31 to complete the brush holder assembly 62i.

It is sometimes desirable, especially with the heavy duty motors, to use a brush 64j, illustrated in FIG. 37, which has a spring 112j mounted between a post 180 and a metallic disc 182 held in position by a wire embedded in the post 180 and soldered to the metallic disc 182. The wire 184 extends upwardly from the post 180 through the inside of the coils of the spring 1l2j to be connected to the metallic disc 182.

In the prior art, in order to avoid turning the metallic disc and connected wire, a downturned finger or ear would extend into engagement with the tube 68, so that turning of the cap 72 would not turn the disc. The present invention eliminates the use of such an extension and permits the metallic disc 182 to be flat. The metallic 182 as illustrated in FIG. 32, is of smaller diameter than the diameter of the internally threaded upper portion 94 of the holder 66. The length of the wire 184 is predetermined to place the spring 112j in slight compression. After the holder 66 and tube 68 have been mounted within the housing 44, the brush 64j will be radially slid into the tube 68 and a retainer 114 placed atop the metallic disc 182. The plunger means l20j having a solid barrel 124j and a flat end 146j from which a plunger 134 extends from the center thereof, is placed into the aperture 116 of the retainer 114. The plunger 134j is approximately twice the thickness of the retainer 114 and will also extend into a central aperture 186 formed in the metallic disc 182. The diameter of the barrel 124j is slightly smaller than the inner diameter of the threaded upper portion 94 of the holder 66. Depressing the plunger means lj within the holder 66 compresses the spring ll2j about the post 180 by radially moving the disc 182 downwardly and forcing the edges 118 of the retainer 114 into engagement with the thread 98 adjacent the bottom of the upper portion 94, as shown in FIG. 33. After removal of the plunger means l20j from the holder 66, the cap 72 will be threadedly connected to the holder 66 to complete the brush holder assembly 62j.

If the size of the holder 66 is sufficiently large, the assembler can dispense with the plunger means 120j, and after placing the retainer 114 atop the upper portion of the holder 66 as illustrated in FIG. 35 of a brush holder assembly 62j, the assembler may use a finger or other projection to depress the retainer 114 within the threads 98 of the upper portion 94 of the holder 66, as illustrated in FIG. 36. Thereafter caps (not shown) would be threadedly received in the upper portion 94 of the holder 66 to complete the assembly.

It will be understood that various changes in the details, materials, arrangements of parts and operating conditions which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principles and scope of the invention.

Having thus set forth the nature of the invention, what is claimed is:

1. Apparatus for retaining a brush in a holder mechanism connected in an electric motor having a commutator, the holder mechanism including a holder having a counterbored inner opening with a threaded upper portion, a tube carried in the holder, a brush radially slidable in the tube in superposition to the commutator, a coil spring connected to the brush and a cap threadedly connected to the holder to compress a spring and bias the same in the direction of the commgtator sa id a pparatus comprising: ,2 e

a. a retainer sizg to sligh tlyoverlap the threaded opening in the upper portion of the holder prior to the cap being screwed in place,

b. the retainer is made of a thin, nonmetallic and semiflexible material,

c. The retainer has a central aperture formed therein,

d. a plunger means operatively associated with the retainer,

e. a barrel means formed on the plunger means, of

smaller cross-sectional dimension than the crosssectional dimension of the retainer,

f. a projection means extending from one end of the barrel,

g. the barrel means to exert a substantially uniform pressure upon the retainer being inserted into the brush holder,

h. the projection means to extend through the central aperture of the retainer upon insertion thereof to be disposed within the coils of the spring to radially align the spring within the holder, and

i. the plunger means, including the barrel means and the projection means, is inserted into the brush holder to force the retainer radially downwardly, wherein the brush contacts the commutator and the spring is compressed between the brush and the retainer, the-retainer will have its edges jammed into the threads of the holder to maintain its position after the plunger is removed prior to the cap being threaded into the holder.

2. The combination claimed in claim 1 wherein:

a. the plunger means includes a barrel and a plunger extending from the flat end of the barrel to engage the coils of the spring to align the spring within the holder during depression of the retainer and compression of the spring, and

b. the retainer has a central plunger extends.

3. The combination claimed in claim 2 wherein:

a. the barrel has a central aperture through which the plunger retractably extends, and

b. the plunger is biased to engage the brush and pass through the spring to centrally align the same within the holder upon compression of the spring by depressing the retainer.

4. The combination claimed in claim 3 wherein:

a. the central aperture of the barrel is counterbored to form an upper chamber,

b. the plunger has an enlarged head disposed in the upper chamber with the plunger extending through the central aperture and out of the flat end,

0. a plunger spring is disposed in the upper chamber to engage the enlarged head'of the plunger and urge it in the direction of the flat end of the chamber to engage the enlarged head of the plunger and urge it in the direction of the flat end of the barrel, and

d. a cover is disposed across the top of the upper chamber to form a top for the opposite end of the plunger spring, whereby upon the plunger means being inserted into the holder the plunger spring will depress and the plunger will be retracted into the upper chamber of the barrel.

5. A brush holder assembly for an electric motor having a commutator comprising:

a. a brush holder having an internally threaded upper portion of predetermined diameter,

b. a tube carried in the holder,

c. a brush radially slidable in the tube to operatively engage the commutator,

d. a coil spring carried on the brush,

e. a retainer extending across the upper portion of the holder by a small predetermined dimension and adapted to be radially pressed into the upper portion of the holder to compress the spring and urge the brush to engage the commutator, whereby the retainer edges will be deflected into the threads of the holder,

f. a plunger means is detachably connected to the retainer to force the retainer into the upper portion of the holder and cause the edges of the retainer to collapse into the threads of the holder, after which the plunger means is removed to permit the screw connection of the cap to the holder,

g. the plunger means includes a barrel having an internal chamber in which is housed a plunger spring which biases a retractable plunger from one end thereof,

h. the retainer has an aperture formed therein through which the plunger extends to be disposed within the coils of the spring,

i. the barrel being inserted into the brush holder to depress the retainer therein, and pennit the aperture in which the plunger to be retracted into the internal chamber of the barrel,

j. a cap screw connected into the upper portion of the brush holder, and

k. the retainer to isolate the spring from the turning motion of the cap.

6. A brush holder assembly for an electric motor having a commutator comprising:

a. a brush holder having an internally threaded upper portion,

b. a tube carried by the brush holder,

c. a brush radially slidable in the tube to operatively engage the commutator,

d. a coil spring having one end disposed on the brush to extend upwardlly therefrom,

e. a retainer sized to have its edges overlap the threaded upper portion of the brush holder,

f. a projection formed in the retainer for constraining the other end of the spring from radial movement within the brush holder,

g. a plunger means operatively detachably associated with the retainer,

h. a barrel means formed on the plunger means of smaller cross-sectional area than the crosssectional area of the upper portion of the brush holder,

i. the barrel means insertable into the upper portion of the brush holder to force the retainer axially downwardly within the brush holder wherein the edges of the retainer will be deformed within the threads of the upper portion of the brush holder to lock the retainer in the depressed position, and permit the plunger means to be removed from the brush holder, while the spring is compressed,

j. a cap screw connected into the threaded upper portion of the brush holder, and

k. the retainer to isolate the spring from the turning motion of the cap.

7. The combination claimed in claim 6 wherein:

a. the projection extends downwardly from the plane of the retainer, and

b. the coils of the spring surround the projection, whereby the spring is retained during depression of the retainer.

8. The combination claimed in claim 6 wherein:

a. the projection extends upwardly from the plane of the retainer, and

b. the coils of the spring seat within the projection to align the spring during depression of the retainer within the holder. 

1. Apparatus for retaining a brush in a holder mechanism connected in an electric motor having a commutator, the holder mechanism including a holder having a counterbored inner opening with a threaded upper portion, a tube carried in the holder, a brush radially slidable in the tube in supersition to the commutator, a coil spring connected to the brush and a cap threadedly connected to the holder to compress a spring and bias the same in the direction of the commutator, said apparatus comprising: a. a retainer sized to slightly overlap the Threaded opening in the upper portion of the holder prior to the cap being screwed in place, b. the retainer is made of a thin, nonmetallic and semiflexible material, c. The retainer has a central aperture formed therein, d. a plunger means operatively associated with the retainer, e. a barrel means formed on the plunger means, of smaller crosssectional dimension than the cross-sectional dimension of the retainer, f. a projection means extending from one end of the barrel, g. the barrel means to exert a substantially uniform pressure upon the retainer being inserted into the brush holder, h. the projection means to extend through the central aperture of the retainer upon insertion thereof to be disposed within the coils of the spring to radially align the spring within the holder, and i. the plunger means, including the barrel means and the projection means, is inserted into the brush holder to force the retainer radially downwardly, wherein the brush contacts the commutator and the spring is compressed between the brush and the retainer, the retainer will have its edges jammed into the threads of the holder to maintain its position after the plunger is removed prior to the cap being threaded into the holder.
 2. The combination claimed in claim 1 wherein: a. the plunger means includes a barrel and a plunger extending from the flat end of the barrel to engage the coils of the spring to align the spring within the holder during depression of the retainer and compression of the spring, and b. the retainer has a central aperture in which the plunger extends.
 3. The combination claimed in claim 2 wherein: a. the barrel has a central aperture through which the plunger retractably extends, and b. the plunger is biased to engage the brush and pass through the spring to centrally align the same within the holder upon compression of the spring by depressing the retainer.
 4. The combination claimed in claim 3 wherein: a. the central aperture of the barrel is counterbored to form an upper chamber, b. the plunger has an enlarged head disposed in the upper chamber with the plunger extending through the central aperture and out of the flat end, c. a plunger spring is disposed in the upper chamber to engage the enlarged head of the plunger and urge it in the direction of the flat end of the chamber to engage the enlarged head of the plunger and urge it in the direction of the flat end of the barrel, and d. a cover is disposed across the top of the upper chamber to form a top for the opposite end of the plunger spring, whereby upon the plunger means being inserted into the holder the plunger spring will depress and the plunger will be retracted into the upper chamber of the barrel.
 5. A brush holder assembly for an electric motor having a commutator comprising: a. a brush holder having an internally threaded upper portion of predetermined diameter, b. a tube carried in the holder, c. a brush radially slidable in the tube to operatively engage the commutator, d. a coil spring carried on the brush, e. a retainer extending across the upper portion of the holder by a small predetermined dimension and adapted to be radially pressed into the upper portion of the holder to compress the spring and urge the brush to engage the commutator, whereby the retainer edges will be deflected into the threads of the holder, f. a plunger means is detachably connected to the retainer to force the retainer into the upper portion of the holder and cause the edges of the retainer to collapse into the threads of the holder, after which the plunger means is removed to permit the screw connection of the cap to the holder, g. the plunger means includes a barrel having an internal chamber in which is housed a plunger spring which biases a retractable plunger from one end thereof, h. the retainer has an aperture formed therein through which the plunger extends to be disposed within the coIls of the spring, i. the barrel being inserted into the brush holder to depress the retainer therein, and permit the plunger to be retracted into the internal chamber of the barrel, j. a cap screw connected into the upper portion of the brush holder, and k. the retainer to isolate the spring from the turning motion of the cap.
 6. A brush holder assembly for an electric motor having a commutator comprising: a. a brush holder having an internally threaded upper portion, b. a tube carried by the brush holder, c. a brush radially slidable in the tube to operatively engage the commutator, d. a coil spring having one end disposed on the brush to extend upwardlly therefrom, e. a retainer sized to have its edges overlap the threaded upper portion of the brush holder, f. a projection formed in the retainer for constraining the other end of the spring from radial movement within the brush holder, g. a plunger means operatively detachably associated with the retainer, h. a barrel means formed on the plunger means of smaller cross-sectional area than the cross-sectional area of the upper portion of the brush holder, i. the barrel means insertable into the upper portion of the brush holder to force the retainer axially downwardly within the brush holder wherein the edges of the retainer will be deformed within the threads of the upper portion of the brush holder to lock the retainer in the depressed position, and permit the plunger means to be removed from the brush holder, while the spring is compressed, j. a cap screw connected into the threaded upper portion of the brush holder, and k. the retainer to isolate the spring from the turning motion of the cap.
 7. The combination claimed in claim 6 wherein: a. the projection extends downwardly from the plane of the retainer, and b. the coils of the spring surround the projection, whereby the spring is retained during depression of the retainer.
 8. The combination claimed in claim 6 wherein: a. the projection extends upwardly from the plane of the retainer, and b. the coils of the spring seat within the projection to align the spring during depression of the retainer within the holder. 